High-voltage direct-current power supply system



Sept. 18, 1951 w, HERQLD 2,568,394

HIGH-VOLTAGE DIRECT POWER SUPPLY SYSrEllS Original Filed June 3, 1947IIIIIIIIIII I ENTOR 00m Wyzvw BY ATII'ORNEY Patented Sept. 18,1951

HIGH-VOLTAGE DIRECT-CURRENT POWER SUPPLY'SYSTEM Edward Herold, Kingston,N. J., assignor to Radio Corporation of America, a corporation ofDelaware Original application June a, 1947', Serial no. 752,009. Dividedand this application May 25,, 1948, Serial No. 29,128

2 Claims. 1

This invention relates to power supply systems for producing high directcurrent voltages suitable for operation of cathode-ray tubes,electrostatic precipitators and the like.

This is a division of my co-pending application, Serial No. 752,009,filed June 3, 1947, now abandoned, and assigned to the same assignee asthe present application.

In general, the object of the invention is to provide a small, light,inexpensive power supply unit directly energizable from a low-voltagepower line and capable of delivering high, direct current voltage toloads having small current requirements.

In accordance with the invention, a single tube operable from alow-voltage source is used,'with a radio-frequency transformer, both asan oscillator generating high-voltage, high-frequency current and as arectifier for the high-voltage so generated. I

More particularly, in one form of the invention, the tube may be atriode whose anode is divided, slotted, or otherwise constructed ordisposed to provide one or more electron paths from the cathode of thetube to rectifier anode structure disposed beyond the triode anode;preferably, for enhanced power output the spacing between the anode andgrid of the triode is small and the mesh of the grid is coarse.

In another form of the invention, the tube may be of the beam-power typewith close spacing between the control grid and screen grid, andpreferably with the corresponding elements of the two grids inalignment. The screen grid is connected to the anode so that theforegoing electrodes function as a triode having high transconductance.The anode is slotted, divided or otherwise apertured to provide one ormore electron paths from the cathode to rectifier anode structuredisposed beyond the triode anode.

The invention further resides in features of construction, combinationand arrangement herein described and claimed.

For a more detailed understanding of the invention, reference is made tothe accompanying drawings, in which:

Figure 1 is an enlarged plan view, in section, of the electrodes of anoscillator-rectifier tube;

Figure 2 schematically illustrates a power supply system using the tubeof Fig. 1;

Figure 3 is an enlarged plan view, in section, of the electrodes ofanother form of oscillatorrectlfier tube;

Figure 4 schematically illustrates a power supply system utilizing thetube of Fig. 3;

Figure 5, in perspective, shows a power sup- 2 ply unit incorporatingthe system of Fig. 4; and

Figure 6 is a side elevational view, in section, of another form ofoscillator-rectifier tube.

For the operation of cathode-ray oscillographs, electrostatic dustprecipitators and the like, high direct-current voltages are required,although the current requirements of such devices are low. The usualpower supplies comprising low-frequency step-up transformers, rectiflersand filter chokes for stepping up the alternating current voltage of apower line is expensive, bulky and heavy. Arrangements have beenproposed for producing the high-voltage direct current by rectificationof voltages developed by a radiofrequency oscillator,'but in generalthey have been unduly expensive or unsatisfactory in operation. Forexample, one type required three tubes, a low-voltage rectifier, anoscillator, and a high-voltage rectifier whereas another form used anunorthodox tube using a plate-like grid remotely spaced from the cathodein avoidance of overheating of the grid or breakdown of the cathode, butin consequence had a mu of less than unity and a correspondingly lowtransconductance.

In contrast therewith and as will later appear,

I the inexpensive, small and light power supplies of this inventioninclude only a single tube which serves both as an oscillator and as ahigh-voltage rectifier and can be operated directly either from analternating current power line or from a direct current power line.

One suitable form of tube Ill, shown in Fig. 1, comprises a cylindricalcathode ll within which is disposed the usual heater (not shown). Thecathode l l is surrounded by a control grid l2 which, except in respectslater mentioned, may be of normal construction; it may, for example,

comprise a round or oval 'helix of fine wire with suitably spaced turns.The oscillator anode I! which surrounds the grid and cathode may be ofcylindrical or oval cross-section, generally in accordance with theusual anode construction, but is provided with two slots 25 which mayextend partially or entirely along the length of the anode parallel tothe cylindrical cathode l l. The electrodes thus far described form atriode having a mu substantially greater than unity. Beyond the openingsor gaps between the two anode sections are disposed the electrodes llwhich comprises the split anode of the high-voltage rectifier section oftube IO.

In operation of the tube, the major part of the total cathode emissionflows to the oscillator anode II and the minor part thereof flows denserI9.

through the gaps 25 of anode I3 to the rectifier anode I4. For enhancedcathode current and correspondingly increased output power at lowoscillator anode voltage, the spacing between the anode I3 and grid I2should be small, as of the order of mm. to 1 mm. and the mesh of thegrid should be similar to that used in power tubes. When it is notfeasible further to reduce the spacing because of danger of shorting,greater output may be obtained by recourse to the tube constructionsshown in Figs. 3 and 6 later described in detail.

A high-voltage power supply circuit using the tube Ill of Fig. 1 isshown in Fig. 2. The windings I5 and I6 form a radio-frequency step-uptransformer I'I, one terminal of whose secondary winding I6 is connectedto the high-voltage'rectifier anode I4 of tube ID. The primary windingI5 of the transformer is tuned by condenser I8 to the frequency at whichthe winding I6 is resonant by virtue of its distributed capacity andother stray capacities effectively in shunt thereto. The

common terminal of the primary and secondary windings of transformer I1is effectively connected to the grid |2 of tube I0, so far asradiofrequencies are concerned, by the blocking con- The other terminalof the primary winding is connected to the cathode II of the tube, sofar as radio-frequencies are concerned, by the by-pass condenser 20. Foroperation of the triode section of tube II) as an oscillator, thetickler coil or feedback winding 2| is inductively coupled to thetransformer I1 and is connected to-the oscillator anode I3 of the tube.

In the series-feed arrangement shown, the oscillator anode I3 isconnected through the feedback coil 2| to the positive terminal B+ of asource of supply voltage whose negative terminal B is connected tothe'cathode of the tube. However, this source of voltage may be a 110volt power line, either alternating or direct; in the former case theoscillator triode section operates as a self-rectifying device.

The tuned primary circuit I5, I8, the feedback coi1 2| and the triodesection of tube It! function as an oscillator, producing across theprimary coil 1 a radio-frequency voltage. By adjustingthe conquencyvoltage, of the order of at least several kilovolts, is produced acrossthe terminals of the secondary winding I6. For each half cycle of theradio-frequency oscillations, the potential of grid I2 swings positivewith respect to the cathode II, and consequently electrons flow from thecathode to the oscillator anode I3 and also through the opening 25, tothe high-voltage rectifier anode I4. For maximum output, the windings I5and I6 are so poled that the high-frequency potential of the rectifieranode I4 is in phase with the high-frequency potential of the oscillatorgrid I2. The direct current passed by the rectifier anode I4 flowsthrough the directcurrent output circuit including the auto transformerI! and the condenser 20 to charge the condenser to a direct-currentvoltage of magnitude closely corresponding with the stepped-up radiofrequency voltage across the secondary winding I6. The highdirect-current voltage available across the condenser 2|] may be appliedto a suitable high resistance load 24, such as the cathode to secondanode circuit of a cathode-ray tube, the plates of a precipitator, orother low- 4 current demand apparatus requiring high direct currentvoltage for its operation.

The direct-current difference of potential between the cathode of thetube and the common.

terminal of the prima:y and secondary windings of transformer I1 is farin excess of the grid biasing potential required for operation of theoscillator section of the tube; the blocking condenser I9, however,prevents application of this potential to the grid I2 and the properoperating potential of the grid is provided by the grid leak 23connected between the cathode II and grid |2.- Condenser I9 must be ahigh-voltage condenser capable of withstanding several kilovolts. Thecathode heater, if of the 110-vo1t type, may be directly connected tothe terminals 3-, 3+ of a power line; if of 'lower voltage type, forexample of the 58-volt type, a suitable series resistor is employed. Thecondenser 22 connected across the terminals B+, 3- serves as a by-passcondenser to prevent the radio-frequency currents of anode I3 fromgetting into the power line and to reduce the radio-frequency impedancethereof. All of the components of Fig. 2 may be packaged as a compactunit similar to that shown in Fig. 5.

In another form of oscillator-rectifier tube 2'5 affording greateroutput, the cathode 21, Fig. 3, is of oval or generally similarcross-section to provide a large electron-emitting area close to theinner or control grid 28. A second or outer grid 29, whose turns arepreferably in alignment with those of grid 28 to reduce the dissipationby grid 29, is spaced very closely from grid 28 to draw relatively highcurrent from the cathode 21 when the grid 29 is positive with respectthereto. The oscillator anode 30 of tube 26, like that of tube III (Fig.1), is divided or slotted, as at 3|, to provide an electron path fromthe cathode 21 to a split high-voltage rectifier anode 32 disposedoutside or beyond the anode 30 in alignment with the cathode and thegaps 3 I. Heat-dissipating fins may also be used on anode 30, ifrequired to allow higher power dissipation. The inner section of thetube is similar to a beam power tetrode, but can be used as a triode asshown in Fig. 4 where the outer grid 29 is connected to the anode 30.The high-voltage rectifier anode 32 is supported at the top of the tube,Fig. 5, and there connected to an externalcap or terminal. The heater,now shown, is disposed within the cathode 21 and is preferably designedto operate directly from the power line voltage, for example, volts,though a lower voltage heater may be used with a suitable seriesresistance.

The tube 26 may be used in the circuit shown in Fig. 2, but ispreferably used in the circuit of Fig. 4. In fact, either tube III or 26may be used in either of the circuits of Fig. 2 or Fig. 4, the latterhaving advantages which will appear in subsequent discussion thereof.

In Fig. 4, the oscillator portion of the power supply comprises thewinding 33 tuned by condenser 36 to the operating frequency, and theelectrodes 21, 28, 29 and 30 of tube 26. The grid section 34 of winding33 is connected between the cathode 21 and grid 28 of tube 26. Oneterminal of the anode section 35 of the winding 33 is connected to thecathode 21 and the other terminal of the winding 35 is connected throughthe radiofrequency by-pass condenser 39 to the oscillator anode 30 andouter grid 29 of tube 26. The inner section of tube 26 and the windings34, 35

thus form an oscillator circuit producing a highfrequency voltage acrossthe winding 33 The winding 33 serves as the primary of a radio-frequencystep-up transformer whose secondary 40 is connected to the high-voltagerectifier anode 32 of tube 26. The windings 33 and 40 are preterably sopoled that the radio-frequency potentlals of the rectifier anode 32 andthe control grid 28 of the oscillator section of the tube are in phase,thus to insure that maximum current is available to the rectifier anode32 at the time of each cycle when rectification occurs.

As the windings 33 and 40, unlike the windings l5 and I6 of Fig. 2, ofthe radio-frequency stepup transformer are now separate, the blockingcondenser 31 is not subjected to the high direct current voltageproduced by rectification of the output of coil 40 and the grid leakresistor 38 may be connected across the blocking condenser to minimizeabsorption of power from the oscillator circuit.

The condenser 36 is adjusted so that the frequency of the generatedoscillations approximately coincides with the natural resonant frequencyof the transformer secondary 40, thus to produce across the secondarywinding a very high radio-frequency difference of potential. The directcurrent resulting from application of this radio-frequency voltage tothe anode 32 of tube 26 charges the high-voltage condenser 4| to adirect current voltage approximately corresponding with theradio-frequency voltage across the secondary winding 46. This highvoltage may be applied to a cathode-ray oscilloscope, dust precipitatoror other high impedance device generically represented by the loadresistor 42.

The high-voltage condenser ll need be only large enough effectively tobypass the radio-frequency, usually several hundreds of kilocycles, butif the oscillator is operated from a 60-cycle line, there will be adecided 60-cycle ripple component in the D. C. output voltage appearingbetween the terminal 55 and ground unless the time constant of condenser4| and the efiective load resistance is large enough to afiordsatisfactory filtering at 60 cycles. If ripple-free high-voltage isrequired, conventional inexpensive resistance-capacity filters may beinterposed between the load and the output terminals in the power supplysystem.

By way of example, a power supply system of the type shown in Fig. 4 andhaving the constants given below delivered 6,000 volts to a 50 megohmload and 4,000 volts to a megohm load when a 120 volt 60-cycle sourcewas connected to the cathode and anode terminals of the oscillatorsection of tube 25. The anode current of the high-voltage rectifiersection is small. of the order of several hundred microamperes,

'whereas the anode current of the low-voltage oscillator section isrelatively high, for example, of the order of to 50 or moremilliamperes. The heater 43 of the tube, if of the 110-volt type, mayalso be directly operated from the same source, although in a particularexample given below the tube had a 58-volt heater in series with aresistor 44.

Coil 33.50 turns; 60/38 Litzendraht wire, tapped at turns, wound inquarter-inch pl, 3 turns per layer.

Coil 40.-2100 turns; 3/41 Litzendraht wire, wound in'l pis. Each pi isinch thick and has 300 turns. Spacing between windings 40 and 33 isinch, between pis, spacing is 1 1; inch.

Condenser 37.0.001 microfarad.

Condenser 41.0.002 microiarad.

Condenser 39.0.1 microi'arad.

, Condenser 36.0.004 microforad (approximate value, should be adjustedfor resonance).

Resistor 38.1000 ohms.

The overall dimensions of the power supply unit 41 incorporating thesecomponents of the system of Fig. 4 are only approximately five inches xtwo inches x six inches, and the unit weighs very little. As shown inFig. 5, the unit 41 may be provided with input leads or cord 45 providedwith a plug for convenient connection to a power outlet 45, Fig. 4, forenergization of the heater and for application of the operating voltageof the oscillator anode. All of the components may be mounted upon orwithin a small metal chassis 48. On the upper side of the chassis 43 ismounted the core or coil-form 49 of suitable insulating material, suchas bakelite or fibre, upon which are disposed the pi-sections formingthe windings of the oscillator and highvoltage transformer. The leadfrom the highvoltage secondary 40 extends to the output terminal 50suitably isolated from the chassis by the standoff insulator 5|. Thehigh-voltage capacitor 4| is of the ceramic dielectric type and isunderneath the chassis, connected to terminal 50. The tube 26, orequivalent, is mounted in' a conventional tube socket 52 disposed in theupper face of the chassis. The external terminal of the high-voltagerectifier anode 32 receives the clip 54 of the lead 53 extending fromthe other end of the high-voltage secondary winding 40. In avoidance ofvoltage breakdown, the high-voltage rectifier anode 32 is supportedwithin the tube 26 only from the top mica element, and large slots arecut in this mica, between the rectifier anode and the electrodes formingthe oscillator section of the tube to reduce leakage.

A still further form of tube suitable for use in this unit, or in eitherof the systems of Figs. 2 and 4, is shown in Fig. 6. In tube 56, thecathode is an elongated cylinder having an upper section 51 and a lowersection 58, both heated from a common heater element 59 disposed withinthe tubular cathode. The lower section of the cathode, the anode 60 andthe grid 6|, are comprised in the oscillator section of the tube. Theupper section 51 of the cathode and the auxiliary anode 62 form thehigh-voltage rectifier section of the tube. The rectifier anode 62 maybe substantially spaced from the triode section and its edges rolled orcurved to minimize sparkover. As in tubes l0 and 25 connections from thelow-voltage oscillator section of the tube extend through the base,Whereas the external connection 63 for the high-voltage rectifiersection extends through the top of the tube envelope 64. All of thetubes [0, 26 and 56, notwithstanding the high voltages involved, aresmall, and, as evident from Fig. 5, approximately the same size asreceiving tubes.

It shall be understood the invention is not limited to the particularcircuits and tubes illustrated, but that changes and modifications maybe made within the scope of the appended claims.

I claim as my invention:

1. A high voltage direct current power supply comprising a dischargetube having at least a first anode and cathode with a control electrodeintermediate between said first anode and cathode, said first anodehaving an aperture in the structure thereof, and a second anode outsidesaid first anode and positioned to receive electron flow through saidfirst anode aperture, a first and second lower impedance windings and athird higher impedance winding electromagnetically coupled with oneanother, connections placing said first winding in series with a circuitbetween said first anode and said cathode, connections applying voltageinduced in said second winding to the control electrode cathode circuitof said discharge tube, the polarity of the winding adjusted to sustainoscillation in said discharge tube, a high voltage output terminal,connections placing said third winding between said output terminal andsaid discharge tube second anode.

2. A high voltage direct current power supply comprising a dischargetube having at least a first anode and cathode with a control electrodeintermediate between said first anode and cathode, said first anodehaving an aperture in the structure thereof, and a second anode outsidesaid first anode and positioned to receive electron fiow through saidfirst anode aperture, a transformer having a first and secondlowimpedance winding section taps and a high impedance winding,connections placing said first low impedance winding taps in shunt withsaid control electrode and cathode, connections placing said second lowimpedance winding taps in shunt with said control. electrode and firstanode, the Doling of said second winding section relative to said firstwinding section being such to produce oscillations in said dischargetube, a high voltage output terminal, and connections placing said highimpedance winding between said high voltageioutput terminal and saiddischarge tube second anode.

EDWARD W. HEROLD.

. REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,823,837 Miessner Sept. 15, 19312,059,683 Farnsworth Nov. 3, 1936 2,104,463 Johnson et a1. Jan. 4, 19382,137,356 Schlesinger Nov. 22, 1938 2,306,888 Knick -1 Dec. 29, 1942'2,373,165 Cawein Apr. 10, 1945 FOREIGN PATENTS Number Country Date528,228 Great Britain Oct. 24, 1940

